function Duck(){


}
//函数表达式
//js变量类型由值决定
var Singleton = function(name){
    this.name = name
}

var obj1 = new Singleton('1')
var obj2 = new Singleton('1')
console.log(obj1===obj2)

var obj = {'a':1}
var obj3 = {'a':1}
var obj4 = obj
console.log(obj==obj3)
console.log(obj==obj4)